The invention relates to a mobile working machine, in particular an automotive concrete pump, having a carrying structure, which is fixed to a vehicle, in particular for a concrete distributor boom, and at least two support legs that are hinge-jointed to the carrying structure via a respective hinge point, wherein each hinge point comprises two bearing plates made from solid material, each provided with a bearing bore and projecting in a forked manner at a lateral distance from each other over the edge of a delimiting wall of the carrying structure, and a hinge pin extending vertically through the mutually aligned bearing bores. The invention additionally relates to a method for producing a hinge point for the support legs of such a mobile working machine.
The hinged coupling of swivel legs to boom pedestals of automotive concrete pumps is similar in its construction to two links of a bicycle chain that are connected to each other via a pin. In this case, the swivel leg or support leg constitutes one “chain link,” the boom pedestal or carrying structure constituting the other. The two parts are connected to each other by the hinge pin such that it is possible for the legs to be swiveled out laterally, about the vertical pin axis. Unlike the bicycle chain, the hinged joint of the swivel leg and the boom pedestal is subject to transverse force and moments transversely in relation to the joint, i.e., in the vertical direction. Accordingly, the bearing link plates are constituted by bearing plates made from solid metal, which conventionally project in a forked manner over a vertical delimiting wall, such that the production requirement is also reduced in comparison with multi-part box-type structures with inserted bushings.
In this context, it must be taken into account that the bearing bores for the swivel-leg pin are usually made in the link plates of the boom pedestal by means of so-called machining centers. These centers are equipped with a suitable drill or milling cutter that is held by a chuck and driven by means of a motor. The tool receiver together with the drive in this case occupies considerably more space than the tool itself. The size of the tool receiver would not matter if the bores were made in the link plates of the boom pedestal from above or from below, since there is sufficient space remaining for the machining appliance above or below the boom pedestal. However, such a procedure would mean rotating the boom pedestal by 180°, since machining centers are very limited in their tool stroke, and therefore the stroke is not sufficient for making the bore from above or below. Rotating the boom pedestal, in turn, means correspondingly elaborate and expensive equipment for fixing the component, or inaccuracies caused by the drilling itself as the bore is being made. However, if the machining appliance moves in the inner region between the link plates of the boom pedestal, and from there machines at least one of the two bearing bores, the hinge pin can be located only so close to the carrying structure of the boom pedestal that there still remains sufficient space for the machining appliance.